With the development of radio networks, data services play a more and more important role in the radio networks, and accordingly require a broader and broader transmission bandwidth. The data services demand a broader bandwidth than voice services do. Especially after the introduction of High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA) and Code Division Multiple Access (CDMA) 1X Do, the transmission rates of the data services that may be provided for the terminals have become higher and higher, and development of the data services has also become faster and faster. Consequently, the traffic load on a base station grows increasingly, and a broader transmission bandwidth is demanded by the base station. In the conventional radio networks, the base stations having three sectors are generally used. After the introduction of HSDPA, HSUPA or CDMA 1X Do, the downlink throughput of the base station may be up to 9 megabits per second (Mbps) and the uplink throughput thereof may be up to 1 Mbps, so as to ensure the data service transmission for the terminals. Plus the overheads of the lower layers, the resulting rate of the physical layer is proximately 15 Mbps in the downlink direction and 1.5 Mbps in the uplink direction. The fees for the data services are relatively low, and thus the income from the data services is greatly less than that from the voice services. In this case, if operators go on to implement the access and data transmission of the base station by using the E1/T1. with expensive rent, their profit is reduced severely.
The x Digital Subscriber Line (xDSL) is a family of technologies that provide very high-bandwidth digital signal transmission over conventional telephone lines and have advantages in convenient access, abundant transmission resources and low transmission cost. At present the xDSL technologies are generally applied in the radio networks. Compared with the accessing of base station by use of E1/T1, the accessing of base station by use of xDSL may reduce the cost in base station access significantly.
It is primarily the Very high speed Digital Subscriber Line (VDSL) and the Asymmetric Digital Subscriber Line (ADSL) in the xDSL family that are used to implement the base station access in the prior art. The two application scenarios are described respectively as below.
FIG. 1 shows a schematic diagram of a networking structure for implementing base station access by use of VDSL in the prior art. It may he seen from FIG. 1 that a base station is connected to a VDSL Modem via an Ethernet line, the VDSL Modern is connected to a Digital Subscriber Line Access Multiplexer (DST AM) via a twisted-pair, and the DSLAM is connected to a Broadband Access Service (BAS) via a fast Ethernet network. The BAS transfers the traffic on the DSLAM to a radio network controller (RNC) via an IP network,
The transmission rate of VDSL in the uplink direction may be up to 1.5 Mbps and in the downlink direction may be up to 12 Mbps. Thus, the bandwidth of VDSL may meet the requirements for data transmission in base station access. However, the valid transmission distance of VDSL is 1 kilometer(km) beyond which the rate of VDSL decreases rapidly. Therefore, VDSL may be only used in short-distance base station access and thus can not be applied widely.
FIG. 2 shows a schematic diagram of a networking structure for implementing base station access by use of ADSL in the prior art. This figure is basically the same as FIG. 1, except that the base station is connected to an ADSL Modem via an Ethernet line and ADSL access technologies are employed therein.
ADSL is applied widely. ADSL has a valid transmission distance up to 3 km and thus is applicable to long-distance base station access. However, because the bandwidth of ADSL is too narrow, i.e. proximately 0.5 Mbps in the uplink direction and proximately 6 Mbps in the downlink direction, the base station access by use of ADSL is unable to meet the requirements of most base stations for transmission bandwidth.